Endometriosis with hemorrhagic ascites in a perimenopausal woman: a case report

Chief complaint: Pelvic fluid discovered for half a year. History of present illness: A 48-year-old perimenopausal Han Chinese woman, married with children, was admitted on 26 July 2025, due to pelvic fluid detected 6 months prior. Computed tomography (CT) and ultrasound 6 months before admission showed a dark area (61 mm diameter) in the pelvis, and 2 days before admission, ultrasound revealed free fluid in the Douglas pouch and both iliac fossae (max diameters 20 mm, 22 mm, 84 mm). She had mild dysmenorrhea for 2 years, without oral pain medication. No loss of appetite or weight loss was reported. Other histories: Past medical history: 2007: Cesarean section. April 2020: Radical thyroid cancer surgery. 7 February 2024: Open uterine myoma excision, bilateral Fallopian tube resection, pelvic adhesiolysis. Both ovaries showed no mass. The uterus was enlarged, with localized adenomyosis features. Family history: No significant hereditary diseases. Treatment history: No history of long-term medication or specific treatments. Social history: No adverse habits; normal social and occupational functioning. Examination findings: Physical examination showed abdominal distension and a palpable cystic-solid pelvic mass (10 cm) with limited mobility. Investigations: 10 July 2025: Anti-Müllerian hormone (AMH) 0.44 ng/ml, follicle-stimulating hormone (FSH) 23.89 mIU/ml; tumor markers [carbohydrate antigen (CA)24–2, CA153, CA125, CA199, human epididymal protein 4] all were within normal range. 25 July 2025: Pelvic magnetic resonance imaging (MRI) showed uterine fibroids, multiple small cystic lesions in both adnexa, and a large amount of pelvic effusion (Fig.  1 ). Fig. 1 Imaging findings. Axial T2WI fat-suppressed sequence images show that the signal characteristics of the hemorrhagic corpus luteum cyst (long white arrow) and nonhemorrhagic corpus luteum cyst (yellow triangle) in the right adnexal area are similar to those in the T2WI non-fat-suppressed sequence images. The distribution range and boundaries of the multiple fluid signals in the pelvic cavity are more clearly displayed than in the T2WI non-fat-suppressed sequence images (blue star). Red arrow is myoma Imaging findings. Axial T2WI fat-suppressed sequence images show that the signal characteristics of the hemorrhagic corpus luteum cyst (long white arrow) and nonhemorrhagic corpus luteum cyst (yellow triangle) in the right adnexal area are similar to those in the T2WI non-fat-suppressed sequence images. The distribution range and boundaries of the multiple fluid signals in the pelvic cavity are more clearly displayed than in the T2WI non-fat-suppressed sequence images (blue star). Red arrow is myoma 28 July 2025: Ascitic fluid cytology: hemorrhagic exudate, no tumor cells. 31 July 2025: Multidisciplinary therapy discussion considered benign or infectious causes. Management: On 1 August 2025, laparoscopic exploration revealed 300 ml hemorrhagic ascites in the pelvis and abdominal cavities. The uterus was slightly enlarged, firm, with palpable nodules, and adhered to the anterior wall of the sigmoid colon and rectum (Fig.  2 ), forming a posterior encapsulated cyst (Fig.  3 ). After incision, thin light red hemorrhagic fluid was released (Fig.  4 ); bilateral ovaries appeared normal (Fig.  5 ). Scattered miliary nodules were seen on the left peritoneum, pelvic wall, and mesentery. Intraoperative frozen section suggested fibrous nodules and endometriotic lesions. Total hysterectomy and bilateral oophorectomy were performed. Fig. 2 The uterus adhesion with the surrounding tissues. Extensive pelvic adhesions with hemoperitoneum. The bowel loops and mesentery are adherent to the posterior uterine wall and the pelvic wall at the uterine fundus level, forming a closed cavity. 1 Uterine fundus (arrow), 2 adherent bowel loops (arrow), 3 bladder (arrow) Fig. 3 Pelvic cystic mass (blue arrow) Fig. 4 Bloody ascitic fluid with open cyst (blue arrow) Fig. 5 Pelvic cavity findings following adhesiolysis. 1 posterior wall of the uterus (arrow), 2 left ovary (arrow), 3 right ovary (arrow), 4 uterine cervix (arrow) The uterus adhesion with the surrounding tissues. Extensive pelvic adhesions with hemoperitoneum. The bowel loops and mesentery are adherent to the posterior uterine wall and the pelvic wall at the uterine fundus level, forming a closed cavity. 1 Uterine fundus (arrow), 2 adherent bowel loops (arrow), 3 bladder (arrow) Pelvic cystic mass (blue arrow) Bloody ascitic fluid with open cyst (blue arrow) Pelvic cavity findings following adhesiolysis. 1 posterior wall of the uterus (arrow), 2 left ovary (arrow), 3 right ovary (arrow), 4 uterine cervix (arrow) 2025-08-07: Pathology confirmed benign cystic lesions and endometriosis (Fig.  6 ). Fig. 6 Postoperative pathology showing endometrial glands (red arrow), endometrial stroma (blue arrow), and smooth muscle (green arrow) Postoperative pathology showing endometrial glands (red arrow), endometrial stroma (blue arrow), and smooth muscle (green arrow) 2025-08-10: The patient recovered well and was discharged. The ascites resolved during following-up. All events are presented in Table  1 . Table 1 Chronological events Date Event description 2024-02-07 Open myomectomy, bilateral salpingectomy, pelvic adhesiolysis 2025-01-06 Gradual abdominal distension; initial pelvic effusion found 2025-07-10 Hormonal and tumor marker tests; all normal 2025-07-25 MRI: uterine fibroids, adnexal cysts, large pelvic effusion 2025–07-31 MDT discussion considered benign or infectious causes 2025-08-07 Pathology: endometriosis 2025-08-10 The patient recovered well and was discharged.The ascites resolved during following-up Chronological events Key points: Preoperative exclusion of malignancy is essential. Definitive diagnosis relies on postoperative pathology. For perimenopausal or postmenopausal women, total hysterectomy with bilateral oophorectomy is recommended. Case summary: The patient had an open myomectomy 1 year ago. Recent laparoscopic exploration revealed an enlarged uterus with features of adenomyosis, extensive pelvic adhesions, hemorrhagic ascites, and multiple small endometriotic nodules. Both ovaries appeared normal without any masses. Pathology confirmed endometriosis.

Endometriosis is defined as the presence of functional endometrial gland and stroma outside the normal uterine cavity to areas such as the peritoneum, ovaries, lungs, rectovaginal septum, and diaphragm [ 1 ]. Endometriosis is a noncancerous, estrogen-dependent disease [ 2 ]. Approximately 10–15% of women of reproductive age have endometriosis, and clinical manifestations vary depending on the location of the endometrial tissue. Approximately 35–50% of women present with dysmenorrhea, pelvic pain, dyspareunia, and infertility [ 3 , 4 ]. In 1954, Brews and colleagues first described endometriosis characterized by hemorrhagic ascites [ 5 ]. Its symptoms are extremely similar to those of ovarian cancer [ 6 ]. To date, the number of documented cases of endometriosis-related ascites does not exceed 100 [ 7 ]. In reports of endometriosis-related ascites, African Americans predominate, accounting for 69.35% of patients, and 16.13% of patients are Asian women; therefore, this condition is very rare among Asian women [ 8 ]. Perimenopausal or postmenopausal Asian women are even less likely to be affected. The literature has reported a case of hemorrhagic ascites in a 60-year-old patient with endometriosis [ 9 ]. Reports of cases in perimenopausal women are rarer. This article presents a case of endometriosis with hemorrhagic ascites in a Chinese perimenopausal woman and summarizes its characteristics to provide some insights for the early diagnosis of this disease.The patient signed an informed consent form.

Hemorrhagic ascites is characterized by a red blood cell (RBC) concentration ≥ 10,000 cells/mm 3 [ 10 ]. The causes of ascites are diverse and include benign or malignant tumors, hemorrhagic pancreatitis, perforated gastrointestinal ulcers, liver cirrhosis, and heart failure [ 11 , 12 ]. In gynecology, ascites is associated with ovarian malignant tumors, ovarian hyperstimulation syndrome, Meigs syndrome, tuberculosis, uterine fibroids, endometriosis, and so on. Hemorrhagic ascites caused by endometriosis often resembles ovarian cancer, with symptoms such as abdominal bloating, pain, decreased appetite, and weight loss. Symptoms associated with endometriosis, such as dysmenorrhea, dyspareunia, and cyclic pain, should be carefully assessed. Its malignant transformation rate is between 0.7% and 1.6% [ 13 ], and it is commonly transformed into endometrioid carcinoma or clear cell carcinoma. Malignant tumors may present as bloody ascites [ 14 ]. The current patient had a 2-year history of mild dysmenorrhea, with no signs of endometriosis. Imaging examinations and tumor markers were unremarkable, and no signs of infection were detected. Therefore, endometriosis-induced ascites was considered preoperatively. After thorough communication with the patient and her family, considering her perimenopausal status, a total hysterectomy with bilateral oophorectomy was planned. Postoperative pathology confirmed the diagnosis of endometriosis. Although magnetic resonance imaging (MRI) and ultrasound examinations can help suggest the possibility of malignant lesions [ 15 ], excluding malignancy is essential. In this patient, preoperative imaging and laboratory examinations did not support the presence of malignant manifestations, with only mild dysmenorrhea observed. A definitive diagnosis of endometriosis can be confirmed only through histopathological examination postoperatively. The mechanism of ascites in endometriosis remains unclear. Spontaneous rupture of an endometriotic cyst may cause peritoneal irritation [ 16 ]. However, this hypothesis may not be universally applicable in cases without ovarian rupture. Another possible mechanism involves sex hormones triggering an inflammatory response in ectopic endometrial lesions [ 17 ]. Some patients present with right-sided pleural effusion (88.5%) and massive effusion (56%), accompanied by symptoms such as dyspnea (67%). When young women develop right-sided hemorrhagic pleural effusion, endometriosis should be considered [ 18 ]. In this perimenopausal patient, no pleural effusion was observed, but young women should be particularly vigilant. After unilateral oophorectomy, the recurrence rate exceeds 50%, whereas bilateral oophorectomy does not result in recurrence. For women who desire fertility, conservative treatment is preferred [ 19 ]. In this perimenopausal patient, bilateral oophorectomy was performed to prevent recurrence, and no recurrence was observed postoperatively. In summary, for female patients who primarily present with hemorrhagic ascites, the first step is to exclude other diseases, particularly malignant tumors. The diagnosis is based on surgical pathology. Treatment methods depend on different ages and fertility requirements. For perimenopausal or postmenopausal women, total hysterectomy with bilateral adnexectomy is recommended to reduce the risk of recurrence and malignant transformation.